Field of the Invention
The invention relates to an apparatus and a method for cleaning a tubular printing blanket.
Offset lithographic web printing presses have printing units containing several cylinders rotating between side walls. The cylinders include a print cylinder carrying a print form having an image thereon and a blanket cylinder carrying a tubular printing blanket. The image is transferred from the print form to the blanket and from the blanket to the web.
Vertical and horizontal web offset presses having gapless tubular blankets may include on-press blanket washers. Such washers are typically integrated into the structure of the press. However, end users of web offset presses often do not purchase on-press blanket washers and therefore manual washing of the blankets must be performed. This results in down-time for the press and accordingly must be performed quicklet leaving little time for inspection. The tubes do not have time to xe2x80x9crestxe2x80x9d and be rejuvenated, thus the use of chemicals on the press is required.
In addition, some presses have limited access for washing the blanket tubes and some washing chemicals are not recommended for use on the press. In such cases, the tubular blankets must be removed for cleaning. U.S. Pat. No. 5,813,336 discloses a printing unit from which print forms and tubular blankets can be removed through an opening in a side wall. The tubular blanket which is removed from the press is then installed into a cleaning station by mounting the tubular blanket on storage chucks. A typical cleaning process comprises rotating the tubular blanket, applying cleaning solution to the outer surface of the blanket and contacting and cleaning the outer surface with a rotating brush. The tubular blankets include an inner thin metal tube which tends to swing and deflect when rotated in the cleaning station and contacted by the rotating brush. This disadvantage increases with an increase of the diameter of the tubular blanket and leads to non-satisfactory cleaning results. Moreover, the interaction of the rotating brush and the flexible tube can further lead to non-elastic deformations of the tube.
It is accordingly an object of the invention to provide an apparatus and a method for cleaning a tubular printing blanket, which overcome the herinafore-mentioned disadvantages of the heretofore-known devices of this general type and which lead to proper cleaning results, specifically when cleaning large diameter tubular printing blankets.
With the foregoing and other object in view there is provided, in accordance with the invention, an apparatus for cleaning a tubular printing blanket, comprising a first end cap mounted to a first end portion of the tubular printing blanket;
a second end cap mounted to a second end portion of the tubular printing blanket; a compressed air inlet passing through the first end cap; a compressed air supply coupled to the compressed air inlet which supplies compress air to the inside of the tubular printing blanket for stiffening the tubular printing blanket during a cleaning operation; and a cleaning element interacting with the outside surface of the tubular printing blanket, for cleaning the tubular printing blanket.
The cleaning apparatus of the present invention has the advantage that the tubular printing blanket is stiffened by the compressed air during the cleaned operation, so that the cleaning element interacts with a resisting, non-swinging and hardly non-deflectable surface of the tubular printing blanket.
In accordance with another feature of the invention, the cleaning element is a rotating brush. In addition, the rotating brush may be rotated by a drive motor or manually by a crank.
In accordance with a further feature of the invention, the first end cap and the second end cap are rotatablay supported, i. e. in a housing of the cleaning apparatus, and one of the first end cap and the second end cap is driven by a drive motor. It is also possible to rotate the end caps manually, e. g. by using a crank.
In accordance with yet another feature of the invention, the rotating brush and the rotating end cap may be connected to a single drive motor via a gear drive.
Pursuant to a further embodiment of the invention, the apparatus comprises at least one cleaning solution applicator for applying cleaning solution to the tubular printing blanket. The cleaning solution applicator may include spray nozzles for applying the cleaning solution to the tubular printing blanket. The cleaning solution may be supplied by a cleaning solution supply.
In accordance with an another exemplary embodiment of the invention, the apparatus may comprise a waste collector disposed below the tubular printing blanket and the rotating brush for receiving the cleaning solution. The waste collector may be part of the housing of the apparatus.
In accordance with a further feature of the invention, a filter and treatment device for receiving the cleaning solution and selectively guiding or recirculating the cleaning solution back to the cleaning solution applicator may be provided. In this embodiment, the reticulation may be achieved via a cleaning solution supply line which also may include a pump.
In accordance with yet another embodiment of the invention, the apparatus may further comprise a biasing element for biasing the first end cap and the second end cap against the associated first end portion and second end portion of the tubular printing blanket. The biasing element may be a pneumatic cylinder or any known actuator, e. g. a lever mechanism with a resilient element acting on the end caps.
According to another embodiment, the biasing element includes a connecting element extending from the first end cap to the second end cap. The connecting element may include a threaded portion which interacts with a nut element arranged at one of the first or second end caps, for clamping the first and the second end cap to the associated end portions of the tubular printing blanket. The nut element may also be formed as an integral part of one of the end caps.
In accordance with a concomitant feature of the invention, the apparatus further comprises a sealing element which is located at the first end cap and preferably also at the second end cap, for sealing the inside of the tubular printing blanket against ambient air.
There is also provided, in accordance with the invention, a method for cleaning a tubular printing blanket, comprising the steps of: mounting end caps to the end portion so of the tubular printing blanket for sealing the inside of the tubular printing blanket against ambient air; supplying compressed air to the inside of the tubular printing blanket for stiffening the tubular printing blanket; and cleaning the outside surface of the tubular printing blanket.
Other features which are considered as characteristic for the invention are set forth in the appended claims.
Although the invention is illustrated and described herein as embodied in an apparatus and a method for cleaning a tubular printing blanket, it is nevertheless not inded to be limited to the details shown, since various modifications and structural changes may be made therein without departing from the spirit of the invention and within the scope and range of equivalents of the claims.
The construction and method of operation of the invention, however, together with additional objects and advantages thereof will be best understood from the following description of specific embodiments when read in connection with the accompanying drawings.